There is a conventional semiconductor light emitting device having a light emitting layer formed by using an AlGaInP-based compound semiconductor for emitting visible light, as disclosed, for example, in Japanese Laying-open Patent Publication No. H4-212479. This known semiconductor light emitting device is structured as shown in FIG. 4. In FIG. 4, the device includes an n-GaAs semiconductor substrate 21. On the semiconductor substrate 21 are epitaxially grown, in order, an n-type cladding layer 22 of an n-type AlGaInP-based compound semiconductor, an active layer 23 of a non-doped AlGaInP-based semiconductor material, and a p-type cladding layer 24 of a p-type AlGaInP-based compound semiconductor. Further, a p-type window layer (current diffusion layer) 25 is epitaxially grown of an AlGaAs-based semiconductor material. On the window layer 25 is formed an upper (p-side) electrode 27 through a p-type GaAs contact layer 26, while a lower (n-side) electrode 28 is formed on a backside of the semiconductor substrate 21. These electrodes 27, 28 are formed of an Au-Ge-Ni alloy or the like.
The light emitting device of this structure is arranged to confine carriers within the active layer 23 sandwiched between the respective cladding layers 22, 24. In order to enhance the light emitting efficiency, the respective cladding layers 22, 24 and the active layer 23 are each determined of a mixed crystal ratio in the AlGaInP-based compound semiconductor, constituting a doublehetero structure.
There have been various proposals on the carrier concentration for the p-type cladding layer 24 of this structure, such as in the above Japanese Laying-open Patent Publication No. H4-212479 which demonstrates that the carrier concentration be preferably 5.times.10.sup.17 -2.times.10.sup.18. However, the n-type cladding layer 22 is formed at a carrier concentration of as high as approximately 1.times.10.sup.18 7.times.10.sup.18 in order to reduce direct-current resistance.